A conventional inkjet printer in the art repeatedly performs a recording operation to eject ink from a recording head to a sheet, while moving the recording head in a main scanning direction; and a conveying operation to convey the sheet in a subscanning direction orthogonal to the main scanning direction by means of a conveying device, in order to form images on the sheet. However, due to manufacturing tolerances in the recording head and conveying rollers of the conveying device used to convey the sheet, an incoincidence may occur between the actual conveying length and the theoretical conveying length. Therefore, this incoincidence is detected prior to shipping the inkjet printer, so that the theoretical conveying length can be calibrated depending on the incoincidence when an actual conveying operation is performed. Therefore, the sheet is fed by the calibrated conveying length to improve quality of the recorded image.
Japanese Patent Publication 2002-283543 discloses an inkjet printer which performs a non-uniform conveying operation for conveying the sheet by unequal conveying lengths for reducing an occurrence of banding (extraneous lines of ink) every time the recording head moves in the main scanning direction. In this inkjet printer, the calibration for conveying lengths is performed each time the sheet is conveyed. Accordingly, the sheet is always fed to a theoretical position.
However, the problem may arise that the calibration for each conveying length is a processing load to the recording operation.
An object of the invention is to provide an image-forming device which reduces a processing load to obtain high image quality.